The present invention relates generally to a method and apparatus for transferring tractor pin feed hole-free web to and from a utilization device normally adapted to drive web using a tractor pin feed arrangement.
In high volume printing applications, laser printers such as the IBM(copyright) 3800(trademark) and 3900(trademark) series, as well as the Siemens(copyright) 2140(trademark), 2200(trademark), and 2240(trademark) series, lay down images on a continuous web by directing the web through an image element, that, typically, comprises a moving image drum having toner deposited thereon. A portion of such a web 12 is illustrated in FIG. 1. The feeding of the web 12 to the image drum is facilitated by one or more xe2x80x9ctractor pinxe2x80x9d feed units that engage evenly spaced holes 14 disposed along opposing widthwise edges of the web on xe2x80x9cpin feedxe2x80x9d strips 16. The widthwise edges having xe2x80x9ctractor pin feed holesxe2x80x9d therein, as well as the sheets themselves often include perforations 17, 18, respectively, for easy removal.
A typical pin feed application is depicted in FIG. 2. A source 20 of continuous web 22 is driven (arrow 24) to an image transfer element 26 of a printer 28. Toner 30 is provided to the image transfer element or drum 26 by operation of the optical print head 32. A separate developer 34 is provided to attract the toner to the drum 26. The web 24 engages the image drum 26 at a transfer station 36 where printing is laid upon the web as it passes over the image drum 26. The image drum rotates (arrow 38) at a speed matched to the speed of web travel. The web 24 is driven to and from the image drum 26 by a pair of tractor units 40 and 42 that each include a plurality of pins 44 on moving endless tractor beds 45 for engaging pin holes in the edges of the web. The pin holes 14 are detailed in FIG. 1 discussed above.
Downstream of the tractor feed units 40 and 42, the web 24 is directed over a fuser 46 and a preheat unit 48 that fixes the toner to the web 24. The web is subsequently directed to a puller unit 50 that comprises a pair of pinch rollers and into a director chute 52 onto a stack of zigzag folded finished web 54.
A significant disadvantage of a printer arrangement according to FIG. 2 is that the additional inch to inch and one half of web that must be utilized to provide the tractor feed hole strips entails significant waste. The web area between the tractor feed pin hole strips already comprises a full size page and, thus, the tractor feed strips represent area having no useful function other than to facilitate driving of the web into the printer. In a typical implementation, the pin holes are subsequently torn or cut off and disposed of following the printing process.
A variety of utilization devices currently employ tractor pin feed continuous web. Such a feed arrangement is a standard feature on most devices that utilize more than 80 pages per minutes. Specialized equipment has been developed to automatically remove tractor pin feed strips when they are no longer needed. Hence, substantial cost and time is devoted to a web element that does not contribute to the finished appearance of the completed printing job. However, such tractor pin feed strips have been considered, until now, a xe2x80x9cnecessary evilxe2x80x9d since they ensure accurate feeding and registration of web through a utilization device.
It is, therefore, an object of this invention to provide a reliable system for feeding continuous web through a utilization device that does not entail the use of wasteful edgewise strips having tractor pin feed holes.
It is another object of this invention to provide a system and method for feeding web that ensures accurate registration of the web with other moving elements of a utilization device and enables web to be directed to a variety of locations.
This invention relates to a system and method for utilizing web that is free of tractor pin feed holes. The system and method comprise the driving of the web along a predetermined path within the utilization device. A web guide is provided in an upstream location from a utilization device element. The guide engages width-wise edges of the web and forms the web into a trough to stiffen the web. A drive roller and a follower roller impinge upon opposing sides of the web and rotate to drive the web through the guide. The drive roller is located adjacent to the guide according to a preferred embodiment. A registration controller is utilized to synchronize the movement of the web with the operation of the utilization device element. The controller includes a drive controller that controls the speed of either the drive roller or the utilization device element to maintain the web and the utilization device element in appropriate synchronization.
In a preferred embodiment, the web guide can comprise tractor pin feed drive assemblies in which the tractor pins include plates that overly the tractor pins. In such an embodiment, web is held in place along its width-wise edges by the overlying plates and is retained against side-to-side movement by the tractor pins. The tractor pins engage the outer edges of the web (rather than holes formed in the edges of the web) and form the web into a trough that provides substantial beam strength to the web and enables accurate guiding of the web through the utilization device element. The drive roller can be located offset from a plane formed by the tractor pin belts to facilitate the formation of the trough.
The drive roller can be interconnected with the tractor pin feed drive element and operate in synchronization therewith. The follower roller of the drive roller can be provided with a pivotal bracket that allows the follower roller to be moved into and out of engagement with the drive roller so that web can be easily loaded onto the utilization device.
The utilization device element can comprise a rotating image drum according to a preferred embodiment and the utilization device can comprise a printer or copier adapted to feed continuous web. The registration controller, similarly, can comprise a sensor that senses a selected mark on the web such as a preprinted mark or a perforation. The controller can be adapted to scan for a mark at a selected time interval and modify the speed of the drive roller based upon the presence or absence of such a mark.
According to a preferred embodiment, the drive motor can include an advance and retard mechanism that is responsive to the controller to maintain the driven web in synchronization with the utilization device element. A registration drive motor and a differential gearing system can be provided to enable advancing and retarding of the drive roller. The drive element can comprise a harmonic drive differential.
The upper, downstream, tractor pin feed assembly of this invention can include a vacuum belt drive that prevents slippage of pinless web under tension applied by various components of the utilization device.
While the term xe2x80x9cdrive rollerxe2x80x9d is utilized according to this embodiment, it is contemplated that a variety of different driving mechanisms that enable advancing of a web to a utilization device element can be utilized according to this invention. It is of primary significance that such devices be capable at advancing a web that is free of tractor pin feed holes along the edges thereof or otherwise thereon. For example, a drive belt or belts can be substituted for the drive roller and the word xe2x80x9crollerxe2x80x9d is particularly contemplated to include such a belt or belts. Similarly, the drive can comprise a full-width roller or reciprocating foot or shoe that advances the web in selected increments.